Method for mechanically recording sound waves in alpha cold way on plane sound carriers that are harder than wax



P 28, 1931. F. w. FREITAG 1,803,050 METHOD FOR MECHANICALLY RECORDING SOUND WAVES IN A COLD WAY ON PLANE SOUND CARRIERS THAT ARE HARDER THAN WAX Filed Dec. 20, 1927 by the aid of a recorder or stylus which pro-- Patented Apr. 28, 1931 UNITED STATES PATENT; OFFICE FELIX WILFRIED FREI'I'AG, OF WERNIGERODE-HARZ, GERMANY METHOD FOR MEOHANIGALLY RECORDING SOUND WAVES IN A COLD WAY 0N PLANE SOUND CARRIERS THAT ARE HARDER THAN WAX.

Application filed December 20, 1927,-Seria1 No. 241,411, and in Germany July 30, 1927.

The methods known heretofore for mechanicall recording sound waves in a cold way may e said to be divided into two groups so far as flat (plate-, or ribbon-like) sound records are used. In accordance with methods of the first group the wave records are ploughed or cut in wax or wax composition duces shavings or chips, such stylus having a leading upright working face. Methods of this group may be called paring methods. Methods of the second group avoid the formation of shavings or chips inherent in paring methods, and replace the paring operation by a pure indentation or impression operation. For methods of the second group there are used sound records which are harder than wax (metal, celluloid-films or the like) and styli, such as describedin the United StatesfPatent 1,373,635, which are characterized in that the working face does not extend vertically to its entire extent, but is interrupted by a surface, which may be provided with a leading edgeby grinding faces thereon. In the stylus used in impressing methods the interruption of the Working face. is a conditio sine qua'non. When the material of the sound record is'forced aside by the stylus on impressing, not only the interrupted part of the working face but also the following vertical portion of the working face lies within the material of the sound carrier. The intention is to interrupt the working face, the working face being composed of a vertical face and one or more faces at right angles thereto constituted by the interruption.

The strictly impression method, however, has not fulfilled expectations. The sound reproduced, it is true, is free from distortions or accessory sounds, but frequently the reproduction is not loud enough. Further, the sound grooves are often not deep enough to permit free guidance of the needle in reproduction, and as, even in reproduction, the

needle must be positively guided, this necessitates the use of a special reproducing device. The subject of the invention is a method of mechanically producing sound grooves in a cold way on plane or flat-sound records harder than wax, which, so to speak, is a mean between the paring method and the impressing method, according to which by theso produced by an impression operation. By

this method asound groove of requisite depth may be formed even in very hard material and the needle vibratory faces thereof soproperly and smoothly shaped as to faithfully reproduce all sounds at any desired or required intensity or volume.

In the first instance it is intended to record the zigzag writing or characters for the production of which, as is known, the stylus is set in vibration by the sound waves transversely of the groove of the sound, record. The result is to impress the side walls of the groove. It is, however, possible, though not as good, to use the hill and dale writing, for the production of which the stylus is caused to vibrate or oscillate perpendicularly to the sound carrier, whereby mainly the base of the grove is impressed, the side walls being partly impressed.

, I have ascertained by experimental re-r search that for the performance of this method the stylus must be given a particular shape. Above all the edges which have a cutting and impressing action must be inclined to the sound record at angles which tending toward the sound record and inclined in the direction of motion of the said record relative to the stylus at an angle of 45 degrees to the face of the record, whereby to effect the scoring or slitting, without excavation, of the sound face of the sound record, the said cutting edge being also formed by unbroken faces, which intersect the same and which form spreading and impressing surfaces arranged at an angle to one another of 98 to 142 degrees in'a plane transverse to the direction of motion of the record relative to the stylus, whereby to effect the expanding and smoothing out of the walls of the slit to form the groove and also to effect the impressing of its side Walls with the sound reproducing undulations.

For explaining the practicable shapes of the stylus and the angular positions of it's cutting edge and its impressing edges sev eral forms of such styli are shown by way of example in the accompanying drawings. All

these styli permit scoring of the'sound carrier to a depth of 1/10 to 2/10 of a. millimeter (according to the hardness of the sound carrier and the load of the sound box), and expansion of thescore into a defined groove and impression of sound reproducing im.- pressions in this groove, while avoiding formation of shavings or chips.

Fig. 1 is a front elevation.

Fig. 2 a side elevation.

Fig. 3 a plan of a. pyramid of triangular horizontal cross section.

The arrow in Fig. indicates the direction in which the cutting edge of the stylus faces, which is opposite to the direction of travel of the sound record it being understood that usually the stylus is fixed and the horizontal sound carrier moved in the opposite direcmay be horizontal or may in certain circum- I tion to that indicated by the arrow.,

The pyramid shown in Figs. 1 to 3 standing on its apex hasa vertical rear face 1 and two side faces 2 and 3. The side faces 2 and 3 intersect at the front cutting edge 4 which is uninterrupted for its entire cutting depth, and intersect the rear vertical face 1 at the point of intersection of the impresing edgesv 5 therewith, which edges 5 are thus positioned to act in a plane transverse to groove of the sound record. The cutting edge 4 effects the scoring or slitting of the face of the sound record and the surfaces 2 and 3 and impressing edges 5 effect the subsequent expanding of the slit into groove form and the smoothing of its walls to provide the reproducing surfaces and indentation. The cutting edge 4 forms an an le a with the face of the sound record which stances deviate from the horizontal. The said angle a, as has been determined by trial, may be within the limits of 1 to 45. 1 The impressing edges 5 contain an angle ,8 which, as has been found experimentally, may vary within the limits eras to 142 degrees. What particular angle 'is tobe preferred depending on the egmposition of the stylus and the sound carrierwill be explained below.

inclined impressing In Figs. and 5 is illustrated a stylus of the form of an inverted pyramid with a rec- FigP4 being a side ground to the form of a quadrangle with theobject of saving material at those parts which are inactive in recording the sound waves. The parallel side walls, which may be perpendicular to the sound record, may bound a figure of rectangular section as 1ndicated in dotted lines in Fig. 5. There thus results a stylus such as shown in Figs. 6, 7, 8 and 9. Fig. 6 being a plan seen' from below, Fig. 7 a perspective view, Fig. 8 a side elevation and Fig. 9 a front elevation. In thesefigures 4 designates the cutting edge, 6-the trailing edge and 5 the impressing edges. As to the angular relation: of these edges to' the sound record the same is true as has been said with reference to Figs. 1 to 5.

In the triangular pyramid according to Figs. 1 to13 the rear face 1 need not beperpendicular to the sound record as shown in .Figs. 1 to 3 but may be inclined forwardly or rearwardly relatively to the sound record. This is illustrated in; Figs. 10, 11, 12 and 13,

If the impressingedges of the stylus shown in Figs. 6 to 9 are inclined forwardly or rearwardlythere result the styli shown in Figs. 14 and 15. In Fig. 14 the impressing edges 5-are inclined forwardly and in Fig. 15 rearwardl The same alteration of the position of t e impressing edges 5 may be effected in the recorders shown in Figs. 4 and I 5. As experience proves by the sound grooves which result from theuse of'a stylus having impressing edges 5 inclined forwardly a louder but not so clear reproduction will be secured, while sound grooves which result from the use of a stylus having rearwardly edges 5 W111 produce a weaker but clearer reproduction.

As has b'een'ex lained above, the an lo a formed between t ecutting edge 4 an the plane of the "face of the sound record must within the limits of 1 to 45 degrees, and the angle ,8 must be within the limits of 98 to 142 degrees. The position of each impressing edge 5 maybe defined in this way of 49 to 71 degrees or with the horizontal an angle of 19 to 41 degrees. The faces 2 and 3 which are bordered by the impressing edges 5 and b the cutting edge 4v may be faceted or bevel ed. Also, when the base of the pyramid has the shape of a rectangle, the faces between the impressing edges 5 and the trail- -ing edge 6.may be faceted or bevelled. In

such a case there results a pyramidical structure which may be of symmetrical or asymmetrical polygonal horizontal cross-section.

The composition of the stylus if not of diamond may be of any other substance as long as it has about the degree of hardness 9.

Thus also corundum composition and stain less steel may be used. The degree of hardness for the material of the stylus may vary between 9 and 10 or more, and correspondingly the above named limits of the angles. Of course, the correct angular position of .the stylus may be determined by correspond- ,ingly inclining the stylus to the sound carrier when the styus is not constructed with the angle described.

The Brazilian black carbon known as Bahia diamond is of maximum hardness at its outer skin, while in its interior it is softer like the Southwest African diamond. The degree of hardness of the skin of the Bahia diamond is nearly attained in synthetic diamonds. If therefore a Bahia diamond is used to form a recording stylus without laying the core open in grinding or if a synthetic diamond is used, the angle on of the cutting edge should be 1 to 5 degrees, while the angle ,3 between the impressing edges should lie between the limits of 137 to 142 degrees on account of the exceedingly great hardness of the substance. If these limits are departed from, the effect aimed at will not be attained.

be 5 to 15 degrees and the angle ;8 127 to 137 degrees.

With the Indian diamond, which is still softer than the Australian, the angle a must be between 15 to 25 degrees and the angle ,8 between 117 and 127 degrees. j

The Southwest African diamond, which is the most suitable for the present purpose,

requires anangle a of 15 to 35 degrees and an angle ,Bbetween 110 and 130 degreesthus allowing of the widest limits within the angle measurements.

The softest diamond, that is, the white or white-spotted Cape-diamond from .the Premier mine, may be ground in thesame manner as the Southwest African diamond. Similar- 1y, natural or synthetic corundum or corundum compositions: or the hardest stainless steel having the degree of hardness between 9 and 10 may be given an angle at upto the highest limits, say up to 45 degrees, while the angle ,8 may be reduced to 98 degrees. 1

Through the above named kinds of diamonds on the average are known with regard to their general degree of hardness, yet there may be variations depending on the localities or mines where they are found; in certain circumstances, and even when they are found at the same place, there may be variations. which make a different angle necessary. Generally speaking, for a material having a degree of hardness between 9 and 10, a

mean value for the angle or of 23 degrees may be allowed, varying about 22 degrees to one or the other side (1 to 45 degrees) and a mean value for the angle ,8 of 120 degrees, which also allows of a deviation to one side or the other of about 22 degrees (98 to 142 degrees).

In certain circumstances the flat sound record or disk, even before being used, may be provided I with grooves in which case the stylus will operate without positive guidance in the same manner as in the use of smooth plane sound records not perviously prepared where the stylus must make its own groove. The scoring and impressing in such case will be effected on the base and against the side walls of the groove, and it is true, in a less effective way, owing to the fact that the stylus must be sunk too deeply because there is a tendency for it to work evenly in the groove in the salne manner as sound recorders having no grooves, and further, because the and then expanding the slit into groove form.

, 2. The method of producing a sound record groove in a record of hard material, which consists in slitting, without excavating, the surface of the material to an effective depth, and then expanding the slit into groove form and simultaneously impressing sound reproducing surfaces therein.

3. The method of-producing a sound record groove in a record of hard material, which consists in slitting, without excavating, the surface of the material to an effective depth, and then expanding the slit into groove form and simultaneously impressing lateral sound reproducing undulations within the same.

' 4. The method of producing a sound record groove in a record of hard material, which consists in slitting, without excavating, the surface of the material to an effective depth, then expanding the slit into groove form and in a cold way in flat surfaced sound records that are harder than wax, which consists-in scoring the surface of the sound record by a sharp edged stylus made of a material having a degree of hardness greater than 9, and then by the action of said stylus expanding the slit thus produced to form a groove and simultaneously impressing therein sound reproducing members.

6. vThe method of forming sound grooves in a cold way in flat surfaced sound records that are harder than wax, which consists in providing a stylus having a sharp cutting edge and side faces intersecting the same and extending divergently therefrom, disposing said stylus so that its cutting edge inclines downwardly and horizontally in one direction at-an angle of substantially to the surface of the record, and producing relative motion between the record and stylus so that the record travels relatively in the direction of the inclination of said cutting edge, whereby ther surface of the record is slit by the cutting edge and the Walls of the slit then expanded into groove form by the diverging lateral faces of the stylus.

7 The method of forming a sound groove in a cold way in flat surfaced records that are harder than wax, which consists in producsubstantially 45 ing relative motion between the record and a portions intersect said sharp cutting edge and diverge therefrom in the direction of relative movement of the record, whereby in the operation of the stylus I edge will slit the surface of the record and the diverging side faces will spread the walls of the slit to form a groove.

11. A recording stylus for producing a sound groove in the surface of a flat surfaced record of hard material, said stylus compris ing a member of substantially wedge shape and made from a material of a degree of hardness greater than 9, and said member being provided with a continuous sharp front cutting edge and two tapering side faces intersecting said edge and diverging rearwardly therefrom, said cutting edge and side faces being in operation inclined at an angle of from 1 to 45 and of relative an les of from 98 to 142, respectively, to the p ane of the surface of the record.

In testimony whereof I have signed my name to this specification. FELIX WILFRIED FREITAG.

stylus made of material having a degree of hardness greater than 9 and provided with a sharp cutting edge inclining at an angle of toward the surface of the record and in the direction of relative motion thereof and with tapering faces diverging from the cutting edge in such direction of relative motion of the record, cutting edge will slit the surface of the record and the tapering faces will spread the walls of the slit to produce a groove.

8.. A recording stylus provided with an operating portion of wedge shape and having a sharp front cutting edge and two ta pering side faces diverging therefrom.

9. A recording stylus comprising a member of substantially wedge shape having a for ward sharp continuous cutting edgeinclining at a downward and rearward angle and two tapering side .faces intersecting said cutting edge at their forward portions and diverging rearwardly therefrom.

10. A recording stylus for producing a sound groove in a fiat surfaced sound record, by relative motion between the stylus and record, comprising a member of sub,-

stantially wedge shape having a forward sharp cutting edge inclining downwardly and in the direction of relative movement of the record at an angle of substantially 45 to the surface of the record, and having two tapering side faces which at their forward whereby the the sharp cutting 

